1. Field of the Invention
This invention relates to a method for making crosslinked vinyl lactam polymers, e.g. crosslinked polyvinylpyrrolidone (PVP) and, more particularly, to crosslinking, by reaction in solution between a stable, crosslinkable PVP copolymer and a functional PVP copolymer at a predetermined pH.
2. Description of the Prior Art
Merijan, in U.S. Pat. No. 3,563,968, described the preparation of functional graft homopolymers of vinyl lactams, e.g. vinyl pyrrolidone, by reaction of polyvinylpyrrolidone with allyl amine or allyl alcohol in ethanol solvent in a bomb reactor at 130.degree.-140.degree. C.
Kitchell, in U.S. Pat. Nos. 4,692,328 and 4,772,484, disclosed the chemical crosslinking reaction of functional graft homopolymers of vinyl pyrrolidone with glutaraldehyde to form a gel which was useful in biological applications.
PVP and PVP copolymers also have been physically crosslinked using E-beam or gamma radiation.
However, it would be of advantage to provide a simple method of crosslinking a stable, crosslinkable vinyl lactam polymer, at a predetermined pH, without requiring condensation with glutaraldehyde, or the use of expensive radiation equipment.